818689661 has 2 divisors, whose sum is σ = 818689662. Its totient is φ = 818689660.

The previous prime is 818689657. The next prime is 818689667. The reversal of 818689661 is 166986818.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 618467161 + 200222500 = 24869^2 + 14150^2 .

It is a cyclic number.

It is not a de Polignac number, because 818689661 - 2² = 818689657 is a prime.

It is a super-2 number, since 2×818689661² = 1340505522056589842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (818689667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409344830 + 409344831.

It is an arithmetic number, because the mean of its divisors is an integer number (409344831).

Almost surely, 2^818689661 is an apocalyptic number.

It is an amenable number.

818689661 is a deficient number, since it is larger than the sum of its proper divisors (1).

818689661 is an equidigital number, since it uses as much as digits as its factorization.

818689661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 995328, while the sum is 53.

The square root of 818689661 is about 28612.7534676410. The cubic root of 818689661 is about 935.4913337450.

The spelling of 818689661 in words is "eight hundred eighteen million, six hundred eighty-nine thousand, six hundred sixty-one".